Twelve days is how long someone with COVID-19 can infect others, according to a study done by teams at Chung-Ang University and Korea University.
They studied 21 COVID-19 patients to see how long the body sheds viable virus.
It took an average of 34 days for a COVID-19 patient to test negative, but within that period, the "viable virus" was detected for a median of 7 days, or 12 at the longest.
The study could provide new guidelines in fighting COVID-19, especially in dealing with clusters.
South Korea reported 336 new cases of COVID-19 on Tuesday of which 295 were local transmissions many of them from clusters at high-risk facilities like hospitals.
The daily average has fallen into the 300s, which is the standard for social distancing level 2, but the authorities are not letting down their guard.
"There was a recent uptick in cases caused by unauthorized church-run schools. It's come down, but this is not the time to say cases are on the decline."
Specifically, cases tied to the International Missions Church are nearing 400 while a cluster spotted a few days ago at Hanyang University Hospital is at 52.
And at Seoul Nambu Correctional Institution, nine new cases were found, a concern because a correctional facility was the source of hundreds of cases earlier this winter.
Though clusters continue to occur at these confined and crowded places, experts say the threat is smaller at schools, which are due to start classes in March.
"For kids under 12 years old, more infections occurred through parents rather than through classmates."
Minors, under 18 years old, have accounted for 8.9 percent of all cases so far, which is far below the average among other generations.
In addition, most cases among young people have been less severe and not as contagious.
This could mean the benefits of closing schools might not outweigh the downsides of depriving kids of time in the classroom.
Kim Do-yeon, Arirang News.